Tuesday, April 22, 2014

Another Hydra option

The "3.0" Hydra boards are due from OSHPark shortly. Those boards are the prototype for the "standalone" variant - that is, a straight-up double-head EVSE (trading the inlet handling circuitry for a GFI and an RTC).

I've done some more thinking about other directions to go.

Chris (the guy at the center of OpenEVSE) is planning a variant of the OpenEVSE board designed to work with contactors instead of 12 volt relays. He also has a very nice custom designed chassis for the OpenEVSE v2 board. He has been adamant that the separate i2c backpack display is more flexible than mounting the display directly on the board. So far, I've done it my way because I've used clear-top cases. That has the advantage of letting you see all the wiring. It also has the disadvantage of, well, showing all of the wiring.

I've sort of had as a point of pride the fact that there are no dangerous voltage levels on the Hydra boards. But if I want, like Chris, to embed contactor drivers on the board, then that's going to have to change.

If I move the display back off the board and re-arrange things, I could make a Hydra board that had an AC input terminal and two contactor terminals segregated in an AC power section of the board. The space given over to the display could instead go to an AC-DC converter to give 3 watts of 5 volt power. A 5v->+/-12 DC-DC module would supply the pilot generator and there would be plenty left for an off-board i2c RGB backpack display and menu/select switch.

I'm not entirely sure I'm going to do this, though. For one, I don't personally have a need for more than 30A of L2, so I don't need contactors (though I know others would). Also, it feels a little like stealing Chris' thunder, though he doesn't currently have a double-headed product. I also have quite a few irons in the fire at the moment, and need to finish some projects before starting on another.

I'd be curious what others think. But then, I'd also love to have lots more people build Hydras.

1 comment:

Portland needs lots of these hardwired hydras. Not enough chargers for the sudden spike in electric cars in the past two years. I had been searching up and down for something like this for the parking garage at work, but must have been googling the wrong words. Then saw the mention on Reddit and found your blog. My problem is the building manager at work tells us that no more EV chargers can be installed because we have no more available breakers. A lot of afternoons I barely make it back home if I didnt arrive to work early enough to snag a charger. So your gadget seems like it would do the trick. I'm not an engineer, but after owning the Leaf have come to seek out better solutions, DIY or not, because vereything on the market right now is super expensive and sucks for the features they all lack. I'd be a buyer if you have a kit that requires no soldering, screwdriver work only. My electrician husband can figure out the rest.